diff --git a/src/calibre/ebooks/metadata/book/base.py b/src/calibre/ebooks/metadata/book/base.py
index 22752ca09e..e3fb8092e6 100644
--- a/src/calibre/ebooks/metadata/book/base.py
+++ b/src/calibre/ebooks/metadata/book/base.py
@@ -159,6 +159,11 @@ class Metadata(object):
         try:
             return self.__getattribute__(field)
         except AttributeError:
+            if field.startswith('#') and field.endswith('_index'):
+                try:
+                    return self.get_extra(field[:-6])
+                except:
+                    pass
             return default
 
     def get_extra(self, field):